@media screen and (min-width: 750px) {
  html {
    font-size: 75px !important;
  }
}
* {
  box-sizing: border-box;
}
body {
  min-width: 320px;
  max-width: 750px;
  /* flexible 给我们划分了 10 等份 */
  width: 10rem;
  margin: 0 auto;
  line-height: 1.5;
  font-family: Arial, Helvetica;
  background: #f2f2f2;
}
html,
body {
  width: 100%;
  height: 100%;
}
